Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)

See vxfsio(7) manual page.
■ By using the cio mount option. The read(2) and write(2) operations occurring
on all of the files in this particular file system will use concurrent I/O.
See “The cio option” on page 43.
See the mount_vxfs(1M) manual page.
Concurrent I/O is a separately licensed feature.
Cache advisories
VxFS allows an application to set cache advisories for use when accessing files.
VxFS cache advisories enable applications to help monitor the page cache and
provide information on how better to tune the page cache to improve performance
gain.
The basic function of the cache advisory is to let you know whether you could
have avoided a later re-read of block X if the buffer cache had been a little larger.
Conversely, the cache advisory can also let you know that you could safely reduce
the page cache size without putting block X into jeopardy.
These advisories are in memory only and do not persist across reboots. Some
advisories are currently maintained on a per-file, not a per-file-descriptor, basis.
Only one set of advisories can be in effect for all accesses to the file. If two
conflicting applications set different advisories, both must use the advisories that
were last set.
All advisories are set using the VX_SETCACHE ioctl command. The current set of
advisories can be obtained with the VX_GETCACHE ioctl command.
See the vxfsio(7) manual page.
Freezing and thawing a file system
Freezing a file system is a necessary step for obtaining a stable and consistent
image of the file system at the volume level. Consistent volume-level file system
images can be obtained and used with a file system snapshot tool. The freeze
operation flushes all buffers and pages in the file system cache that contain dirty
metadata and user data. The operation then suspends any new activity on the file
system until the file system is thawed.
The VX_FREEZE ioctl command is used to freeze a file system. Freezing a file system
temporarily blocks all I/O operations to a file system and then performs a sync
on the file system. When the VX_FREEZE ioctl is issued, all access to the file system
73Veritas File System I/O
Cache advisories